A conventional electric drying apparatus (such as clothes drying machine or bowl drying machine) normally uses a timer to control the drying time. Normally, the drying time is fixedly set by the user according to his judgment so that the drying apparatus will stop the drying operation when the set time has expired. This kind of drying apparatus is not capable of determining whether the articles to be dried are sufficiently dried, when the pre-set drying time is reached. Therefore, conventional electric drying apparatus have the following drawbacks:
(1) Automatical control of drying is impossible. If the drying time is set at a range which is excessive long, one shall have to frequently open the drying apparatus to check if the articles have been sufficiently dried. If the drying time is set at a range which is excessive short, after the drying apparatus is stopped the articles to be dried may not yet be sufficiently dried, and the user will have to turn on the machine and reset the drying time again. Therefore, high efficiency becomes impossible.
(2) When drying a small volume of articles (especially clothes), the drying degree of the articles is unequal. Due to the fact that the drying time cannot be shortened in proportion to the small volume of articles, the conventional apparatus will use more energy.
Further, when using a clothes drying machine to dry a large volume of clothes, the clothes may block the exhaust hole during the revolving of the cylinder, such that the hot air stream (shown by arrows in FIGS. 1-3) is scattering inside the revolving cylinder (as shown in FIG. 3), because it has no where to go. At this moment, the utilization percentage of the heat energy reached its maximum. Because the evaporated moisture is increasing, a wider exhaust hole is required to permit the humid air to be completely exhausted from the drying machine. When drying a small volume of clothes, the exhaust hole is smoothly opened and will not be blocked by the clothes. At this moment, the clothes may stick to the inner surface of the revolving cylinder so as to rotate with the revolving cylinder when clothes rotate with the revolving cylinder, the clothes can rotate as much as 180.degree. (right upper position) and then drop from the right upper position and "intersect" with the hot air stream. At this moment, the effective utilization of heat energy reaches to a minimum. This is because the evaporated moisture is relatively reduced and even though the exhaust hole is smoothly opened, the hot air stream does not fully fill the revolving cylinder (as shown in FIGS. 1 and 2). An effective drying process is achieved only when the clothes and the hot air stream intersect. Therefore, the drying time cannot be shortened or even must be extended when drying a small volume of clothes at one time. Because less moisture is evaporated and mixed with the hot air stream which is expelled from the drying machine, the expelled or exhausted air contains a relatively low percentage of humidity. In other words, although the detected relative humidity is low, the clothes are still wet.
The main object of the present invention is to provide an electric drying apparatus automatic controller to control the performance of the electric drying apparatus to fully utilize the heat energy provided, so as to dry equally any volume of articles put therein within a shortest period of time and in a power resource saving manner.
Other objects and features of the present invention will be fully understood from the following detailed description in connection with the annexed drawings as hereunder.